A United States senator has apologised for making racial remarks at a campaign rally about an Indian-origin man working for a rival Democrat candidate, a media report said on Tuesday.

At a campaign rally in southwest Virginia on Friday, Republican Senator George Allen had pointed to 20-year-old S R Sidarth and repeatedly referred to him as 'macaca.'

"This fellow here with the yellow shirt, macaca, or whatever his name is� He is with my opponent. He's following us around everywhere. And it's just great," Allen had said.

Macaca refers to a monkey that inhabits the Eastern Hemisphere. In some European cultures, macaca can also be taken as a racial slur against African immigrants. "Let's give a welcome to macaca, here. Welcome to America and the real world of Virginia," Allen had said.

Sidarth, an active Democrat, had been assigned to trail Allen with a video camera to document his travels and speeches for rival James Webb, a common campaign tactic. Allen told the Washington Post on Monday night the word macaca had no derogatory meaning for him and he was sorry.

"I would never want to demean him as an individual. I do apologise if he is offended by that. That was no way the point," he said.

But the apology did not mollify Sidarth who said Allen apparently singled him out because his was the only non-white face among 100 Republican supporters.

'I think he was doing it because he could and I was the only person of color there and it was useful for him in inciting his audience,' Sidarth told the daily, adding, 'I was annoyed he would use my race in a political context.'

Steve Mukherjee, a spokesman for the Washington chapter of the Association of Indians in America, said Allen's comments were 'hurtful' and chided the senator for not being more sensitive. 'The world is so volatile and so delicate. You have to be careful what you say and how you say it. The US is no longer black and white,' Mukherjee told the daily.

"What it (macaca) means, I don't know. But it's going to cause him (Sidarth) some grief," he added.

'The kid has a name. This is trying to demean him, to minimise him as a person,' the report quoted Todd as saying, adding: 'The use of macaca, whatever it means, and the reference welcoming Sidarth to America were clearly intended to make him uncomfortable.'